bug repellent

Black flies, ticks, mosquitoes, and other biting insects can turn the most peaceful outdoor paradise into a stressful tormenting nightmare. In this post I’ll discuss the bug repellent strategies and gear that have worked for me as well as those that are recommended by the CDC, and that are registered with the EPA (after being shown to be both safe and effective for human use in repelling ticks and mosquitoes).

1. Cover up

Wearing long-sleeves, long pants, and gaiters in an attempt to keep the mosquitoes at bay hiking through the high sierra during my PCT thru hike.

The first step in keeping the insects at bay is to minimize the amount of skin the buggers have access to by wearing long-sleeved shirts, long pants, socks, gaiters, and closed-toe shoes. This is fairly effective at keeping ticks from biting you, but as many of us have discovered, mosquitoes have an impressive ability to bite through clothing. Constantly wearing head-to-toe rain gear is an effective way to keep the biting insects at bay, but when the weather is hot and humid wearing rain gear as bug repellent is just a different kind of misery. Instead, I move on to option #2…

My thoughts: wearing long-sleeved shirts, socks, long-pants, ultralight gaiters, and closed-toe shoes is just a start. For repelling ticks I highly recommend using permethrin-treated clothes as described in section 2. For black flies, be sure to include a head/bug net. For mosquitoes, add a an EPA-registered and CDC-approved skin-applied bug repellent as described in section 3.

2. Wear Permethrin-Treated Clothing

Permethrin is based on the naturally occurring insecticides found in chrysanthemums.

Permethrin is a man-made synthetic insecticide based on the naturally occurring insecticides (pyrethroids) found in chrysanthemums. It kills insects and anthropods (eg ticks) that come in contact with it by affecting their nervous systems (neurotoxin). According to the centers for disease control and prevention (CDC), “permethrin-treated clothing repels and kills ticks, chiggers, mosquitoes, and other biting and nuisance arthropods.”

0.5% permethrin: EPA-registered for treatment of clothing for human use

When applied to clothing, permethrin binds tightly to the fibers of the clothing (especially cotton clothing). Since permethrin is not water soluble, it remains bound to clothing through repeated washing cycles and is not readily transferred to your skin if/when the garment gets wet. Note that permethrin kills ticks/mosquitoes on contact, so does not prevent bugs from landing on you. As a result, permethrin-treated clothing works best when it is loosely fitting.

The two CDC-recommended and EPA-registered methods approved for permethrin-treated clothing are factory-permethrin treatment and self-permethrin treatment.

Effectiveness (5/5): I carry/wear this mesh jacket for all of my hot weather backpacking and kayaking adventures. It protects me from both mosquitoes and excess exposure to sun. I give this jacket my highest recommendation. It remained effective against mosquitoes for about 1 year of heavy use (I didn’t count the # of laundering cycles). I used it on the PCT, kayaking in Maine during black fly season, hiking all over New England during mosquito season, and trekking through Peru in temperatures up to 112F.

Durability (5/5): The mesh has held up well under brutal thru-hiker treatment and ongoing use. After the factory-permethrin treatment wore off, I have self-permethrin treated the jacket and continue to use it for all my desert/hot climate adventures.

Effectiveness (5/5): Both in the US and abroad I’ve found these pants to be effective at preventing bug-bites. For example, while my cohort in Peru ended up getting eaten alive with red welts all over their legs I remained bug-bite free.

Durability (1/5): These are great travel pants for hot weather, but not so good for brutal backpacking use: the butt of the pants shredded after less than a month of use during my PCT thru-hike.

Self-Permethrin Treatment

If you apply permethrin yourself you have the option of either spraying it on to you clothing/gear or soaking your cloths in it. The CDC recommends treating “clothing and gear, such as boots, pants, socks and tents with products containing 0.5% permethrin,” and treating items “at least 24–48 hours in advance of travel to allow them to dry.” Note: According to the EPA: “Permethrin repellent products used for factory-treatment of clothing or as spray-ons for clothing are not to be applied to certain clothing such as underwear.”

Spray-on application method (~4/5): I use it on gear items for tick protection. I don’t have a good metric for effectiveness of my treated gear, but it seems to work. The gear I treat with spray-on premerthin, with the amount of premethrin I used to treat it in parentheses, includes:

hiking boots & camp shoes (~ 3 oz for both)

sleeping bag (~6 oz)

backpack (~ 3 oz)

tent body (~ 6 oz)

Soaking application method (5/5): I use it for clothing items for both tick and mosquito protection. I soak my clothing items in 0.5% permethrin (using the method described in the section-hiker post linked here) to treat my cloths because I am skeptical about getting complete coverage of my clothing using the spray-on method. My self-permethrin treated clothing seems to keep its protective properties through 6-10 washes. The clothing I treat by soaking it in permethrin, with the amount of premethrin I used to treat it in parentheses, includes:

My Thoughts About Permethrin: Factory-permethrin treated clothing keeps its repellence 5-10 times longer than self-permethrin treated clothing and is worth it to me for my super-lightweight summer clothing. As far as I can tell, permethrin-treated clothing is the best product out there for preventing tick bites. For mosquito repellency the situation is less clear. Permethrin kills mosquitoes on contact, and does not actually act as a repellent, which means that the mosquitoes land on you (and may bite you) before they die. For loose-fitting clothing permethrin works fairly well against mosquitoes, but it is much less effective when used on tight-fitting clothing made from thin fabrics. As a result, I recommend purchasing 1 size larger than normal to maximize effectiveness of permethrin-treated clothing for preventing mosquito bites. Also, according to the CDC mosquitoes in some areas (such as Puerto Rico) have developed resistance to permethrin!

Other repellent treatments for clothing: DEET (EPA-registered) and picaridin (EPA-registered) may be applied to clothing, but they provide shorter duration of protection (same duration as on skin) when compared to permethrin, and must be reapplied after laundering. Both DEET and picaridin are repellents that can be applied to clothing that has been treated with permethrin to provide added protection. Note that DEET may damage plastics and some types of fabrics. I recently experienced this when the small bottle of 100% DEET in my pack leaked, melted through its cap, and fused itself to my bug net in a scary mess.

3. Use Bug Spray (Skin-Applied Repellents)

The bug repellent picaridin is based on piperidine, a compound found in black peppercorns.

The CDC and EPA recommend using skin-applied bug repellents (wearing bug spray) in addition to using permethrin-treated clothing. The question then becomes, which bug repellent should I use? Since bug repellents are classified as pesticides, the EPA is in change of regulating them. Skin-applied bug repellents whose safety and efficacy data meet EPA standards are given an EPA-registered status. EPA-registered repellents can be classified as either conventional repellents, biopesticide repellents, or natural repellents.

Conventional repellents

Conventional repellents are synthetic repellents that directly kill or inactivate pests. The two conventional repellents that are both EPA-registered and CDC-recommended are DEET and picaridin. DEET and picaridin have the longest-lasting repellent effects of all of the skin-applied bug repellents evaluated and registered by the EPA.

DEET in concentrations of 5% to 99% is EPA-registered and approved for direct application to human skin. Unlike permethrin, DEET doesn’t kill mosquitoes or ticks, it just makes it hard for them to smell/detect us, and therefore less likely to bite us. Although the court of public opinion is convinced that DEET is horribly toxic, the EPA believes that it is safe for use as instructed at all concentrations, and for children and adults of all ages. Note that DEET may decrease the SPF of sunscreen and it may dissolve plastics and some fabrics.

My Thoughts About Conventional Repellents: I hate having to apply bug repellent directly to my skin, but on my thru-hikes (and other adventures) I carry a small bottle of 100% DEET for emergency bug-repellent use. DEET has worked well when I needed it, except for one stretch of the PCT where the mosquitoes were impressively aggressive and to my surprise seemed to be DEET-resistant; I applied 100% DEET and they bit me anyway. Although I didn’t know it at the time, it is scientifically possible that the mosquitoes in question were in fact DEET-resistant. After doing the research for this post, I’m going to give picaridin a try.

Biopesticide Repellents

Biopesticide repellents are naturally derived repellents, which are generally considered less toxic than conventional pesticides. It is also important to note that biopesticide repellents don’t need to stand up to the same degree of rigor as conventional pesticides to gain EPA-registered status. There are two EPA-registered and CDC-recommended biopesticide repellents: oil of lemon eucalyptus, aka PMD (p-Menthane-3,8-diol) and IR3535 (the active ingredient in Skin-So-Soft).

IR3535 is the EPA-registered bug repellent in modern Skin-So-Soft bug repellents. It is important to note that the Skin-So-Soft bath oil that was used as bug repellent in the ’90s does not contain IR3535. I remember the Skin-So-Soft bath oil as bug repellent as being woefully inadequate to the task, but have not tried the Skin-So-Soft containing IR3535. Although IR3535 is EPA-registered, the only commercially available forms I was able to find are combined with sunscreen, and the CDC does not recommend the use of combined sunscreen/bug spray products because sunscreens typically need to be applied more often than bug sprays alone. It’s also important to note that the toxicity profile for IR3535 is similar to that of conventional bug sprays. IR3535 is commercially available as: Skin So Soft Bug Guard Plus IR3535 Expedition SPF 30.

Although the following natural repellents (classified as biopesticides) require frequent re-application, and are not recommended by the CDC, they are registered with the EPA as being safe and effective:

My Thoughts About Skin-Applied Pesticides: After looking at all of the repellent options currently EPA-registered and CDC-approved I’m going to switch from 100% DEET to 20% Picaridin. The improved safety profile of picaridin compared to DEET as well as the promise of greater efficacy against black flies and longer duration of protection have convinced me to give it a try. At first glance the biopesticides, especially the Oil of Lemon Eucalyptus sounded promising, but on closer review the fact that they can claim a connection to naturally occurring pesticides isn’t enough to convince me that they are safer than the conventional repellents and the need to reapply them more frequently makes them a poor choice for me. If you’re looking for a second opinion, the EWG guide to repellents list the pros and cons associated with the different repellent options. Whichever bug repellent you choose, be sure to check the concentration of the active ingredient and to read/follow the application directions carefully. Which bug repellents have your tried? Comment and let me know which ones have worked (or failed to work) for you.

4. Know your enemy!

Avoid the biting bugs by learning to love winter!

Know when and where the biting bugs are most active, and try to avoid them. Let’s start with when. The biting insects tend to be most active during the same seasons that people are most active: the spring in summer months. Below is some general information about the when and where for some of the most pesky biting bugs.

What attracts them? Carbon dioxide from your breath, heat, and and other compounds secreted in our sweat and found on our breath.

Areas to avoid: swampy areas and areas with standing water; mosquitoes lay their eggs in standing water

Ticks

Season: whenever temperatures are above freezing (32F), although they tend to be most active April to September. Ticks are least active when temperatures are below 32F and during droughts

Most active time of day: during the most humid part of the day; ticks need moisture to survive, especially the tiny and troublesome nymphs. As a result, nymphs are most active at night and during the mornings on hot days.

Added advice: shower as soon as you return from your outdoor adventure, do a tick check, wash your clothing in hot water, and remove ticks promptly

Additional Thoughts: In addition to avoiding the buggiest areas in the buggiest times (e.g. hiking in the snow), I’ve found that hiking faster (>2 miles/hr) prevents the majority of black flies and mosquitoes from landing on me and biting me. It turns out that mosquitoes typically fly at 1-1.5 miles/hour (1.5 miles/hr), so the little data I was able to find supports the anecdotal evidence that I can outrun most mosquitoes!

5. Dealing with the Itch

Young Patches playing in the mud.

Slightly older Patches boating with her brothers in the backyward.

When I was a kid loved playing in the swamp down by the river, which meant that I’d frequently come home covered in both mud and bug bites. The itchiness would drive me nuts, so I started experimenting with things in the first-aid cabinet that might take the itch away: “after bite”-didn’t work, benadryl cream-didn’t work, calamine lotion-didn’t work, toothpaste-didn’t work, and then I tried IcyHot. It worked!! IcyHot completely masked the itch. I then discovered that if I hadn’t scratched the bite before applying the IcyHot, the bug bite would disappear by the time that the IcyHot wore off… I’d found a bug bite cure!

My Thoughts on IcyHot: As an adult I’ve realized that bug bite prevention works better than carrying IcyHot with me everywhere I go (and constantly coating myself in it), but when my bug bite prevention methods fail and I have a bug bite that’s driving me nuts I still head to the medicine cabinet and treat it with IcyHot.

Summary

When it comes to avoiding ticks and Lyme disease my basic strategy is to:

(while in civilization) Do tick checks and shower after returning from each hike/outdoor activity in tick-infested areas

Avoid unleashed dogs (they run through the tall grasses and bring the ticks back to me)

For mosquitoes, I try to avoid the skin-applied repellents, but when the mosquitoes/black flies are particularly irritating I end up including them. My mesh Bugs Away jacket is a godsend in hot, humid weather. For mosquitoes my basic strategy is to:

Cover up with long-sleeves, long-pants, and gaiters

Use permethrin treated clothing

Hike faster! I’ve found that mosquitoes and black flies don’t tend to bite me when I’m hiking at >2 miles/hr

Use EPA-registered and CDC-approved repellent on exposed areas (hands, ankles, neck/face) sparingly as needed; I typically carry/use DEET, but will be trying out 20% picaridin.

Use a head/bug net in extreme circumstances, especially when the gnats dive-bomb my eyes, fly up my nose, and start swarming so thickly that I inhale the dang things… For gnats I also use the thru-hiker trick of poking a tall blade of grass/wheat out of my hat since they seem to be attracted to the highest moving point; it seems to help a little, but is much less effective than a properly positioned high quality bug net.

Combining these strategies seems to work for me with most biting insects most of the time. The one glaring exception is horse flies. Horse flies are relatively undeterred by repellents, and will bite any exposed flesh they can find. When I’m in an area horribly overrun with horseflies my strategy is to either to dive into the closest body of water and go for a swim (staying under water as much as possible) or to dive into the safety and security of my tent for a nap.